Power measurement device for a bike trainer

ABSTRACT

Systems and methods for accurately measuring power output of a cyclist using a bike trainer that may be operated by a user for stationary riding when coupled to a conventional bicycle. The systems utilize a power output equation that models power due to resistance of a fan of the bike trainer as well as power due to kinetic energy of the fan. The systems account for operating conditions that affect the power measurements so that more accurate measurements can be provided, thereby improving the training experience of the user. Operating conditions include mechanical drag, temperature, humidity, and atmospheric pressure and/or altitude. The power output equation is dependent on the angular velocity of the fan of the bike trainer and the measured or received operating conditions.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention is directed generally to exercise devices, and more particularly to devices that measure power output of users operating bike trainers.

2. Description of the Related Art

Bike trainers (or “bicycle trainers”) have been used by bicycling enthusiasts to support their bicycles for stationary riding. Rather than ride in cold, hot, or rainy weather, a cyclist may use the trainer to ride indoors and obtain an aerobic, cardiovascular workout. Bike trainers also obviate the need for purchasing a separate stationary bicycle for persons who want to occasionally workout while, for example, reading or watching television.

A typical bike trainer has a frame onto which a user mounts a bicycle. The rear wheel of the bicycle contacts a roller or like mechanism connected to a resistance unit. Resistance to the rotation of the rear wheel may be adjustable. In addition, it would be desirable for a resistance unit to provide increased resistance as the rotation of the wheel is increased, so that more energy is required to pedal the bicycle and the rider receives a greater workout.

Training using a power measurement device (“power meter”) is becoming increasingly popular. In general, a power meter is a device on a bicycle or bicycle trainer that allows measuring of the power output of the rider. Power meters may include a computer (e.g., mounted on a handlebar) that displays information about the power output generated by the rider such as instantaneous, maximum, and average power. Power meters provide an objective measurement of real output that allows training progress to be tracked very simply—something that is more difficult when using, for example, a heart rate monitor alone. Power meters provide feedback to the rider about their performance and measure their actual output. Therefore, an athlete performing “interval” training (e.g., alternating intervals of high-intensity training and low-intensity training) using a power meter can instantly see that they are producing 250 watts, for example, instead of waiting for a heart rate to climb to a certain point. Additionally, while an athlete who is not rested or not feeling entirely well may train at their normal heart rate, they are unlikely to be producing their normal power—a heart rate monitor will not reveal this, but a power meter will. Since power meters are used by athletes to provide feedback while training, it is desirable for power meters to provide accurate and consistent measurements.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)

FIG. 1 is a right side view of a bike trainer attached to a conventional bicycle.

FIG. 2 is a right-front perspective view of the bike trainer with the fan housing and covers installed.

FIG. 3 is a left-front perspective view of the bike trainer with the fan housing and covers installed.

FIG. 4 is a right-front perspective view of the bike trainer with the fan housing and covers removed.

FIG. 5 is a left-front perspective view of the bike trainer with the fan housing and covers removed.

FIG. 6 is a right side view of the bike trainer with the fan housing and covers removed.

FIG. 7 is a left side view of the bike trainer with the fan housing and covers removed.

FIG. 8 is a rear view of the bike trainer with the fan housing and covers removed.

FIG. 9 is a front view of the bike trainer with the fan housing and covers removed.

FIG. 10 is a left-rear perspective view of the bike trainer attached to the conventional bicycle, wherein a power console unit is coupled to the handlebars of the bicycle and a velocity sensor is coupled to the bike trainer.

FIG. 11 is a perspective view of the power console unit shown in FIG. 10.

FIG. 12 is a left-front perspective view of the bike trainer and the velocity sensor shown in FIG. 10.

FIG. 13 is a block diagram of the power console unit and the velocity sensor shown in FIG. 10.

FIG. 14 depicts a process for measuring the power output of a cyclist operating the bike trainer using the power console unit and the velocity sensor.

FIG. 15 depicts a process for empirically determining a power equation as a function of various expected operating conditions.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is directed to systems and methods for measuring power output of a cyclist using a bike trainer that may be operated by a user for stationary riding when coupled to a conventional bicycle. The systems disclosed herein account for environmental conditions that affect the power measurements so that more accurate measurements can be provided, thereby improving the training experience of cyclists. Initially, with reference to FIGS. 1-9, a bike trainer 10 that may be operated by a user for stationary riding when coupled to a conventional bicycle 100 is described. Afterward, with reference to FIGS. 10-15, exemplary systems and methods for measuring output power of a rider using the bike trainer 10 are described.

Bike Trainer

Advantageously, the bike trainer 10 includes features described below that simulate the “feel” of riding a moving bicycle by providing resistance and inertia similar to that of a bicycle when operated on a flat paved road surface. The bike trainer 10 also includes features that permit simple coupling and decoupling to the bicycle 100, which allows users to easily use the bike trainer 10 without requiring a time consuming setup process. As an example, users may wish to use the bike trainer 10 when weather conditions are not conducive to riding outdoors, or when locations to ride a bicycle are otherwise undesirable or unavailable. Further, the bike trainer 10 is configured to support a user of the bike trainer in a fashion such that the user is sturdily supported without having to worry about losing his or her balance.

FIG. 1 is a right side view of the bike trainer 10 when coupled to the bicycle 100. The bike trainer 10 includes a first pulley 12 (or drive member) that is rotatably coupled to a laterally extending axle 23 (see FIG. 8) proximate to an upper portion 44 of a frame 40. When the bike trainer 10 is coupled to the bicycle 100, the first pulley 12 takes the place of the rear wheel of the bicycle. In this regard, the rear dropouts 106 of the bicycle 100 are removably coupled to the axle 23 which is secured by an axle clamp 24 and an axle clamp adjustment 22 (see FIGS. 2 and 3), which may collectively be referred to as a “quick release skewer.” The first pulley 12 is coupled to a pulley hub 32 which is best shown in FIGS. 8 and 9. A cassette 26 is positioned over the pulley hub 32 and includes a freewheel mechanism or “freehub” housed therein. The cassette 26 also includes a first sprocket 28 and a second sprocket 30, although it will be appreciated that the cassette 26 may include several sprockets (e.g., 1 to 12 sprockets, or more) of varying sizes having a varying number of teeth. The cassette 26, freehub 32, and first pulley 12 are removably and rotatably secured to an upper portion 44 of the frame 40 using a hexagonal nut 25 (see FIG. 2).

To use the bike trainer 10, a user first removes the rear wheel of the bicycle 100, secures the rear dropouts 106 of the bicycle to the bike trainer 10, tightens the axle clamp adjustment 22, and aligns a chain 104 of the bicycle with one of the sprockets of the cassette 26. In operation, the cassette 26 works with a rear derailleur 108 of the bicycle 100 to provide multiple gear ratios for a user of the bike trainer 10. As can be appreciated the freehub 32 includes a conventional freewheel mechanism that allows a user of the bike trainer 10 to stop pedaling whilst the first pulley 12 is still in motion, which simulates the feel of “coasting” on a moving bicycle. That is, the freewheel mechanism includes a first portion engaged with the first pulley 12 and a second portion engaged with the cassette 26, such that the freewheel mechanism is operative to disengage the first portion from the second portion when the first portion rotates faster than the second portion as would be the situation if the bicycle 100 was moving in a forward direction.

In some embodiments, an adapter (not shown) may be provided to allow various custom or “off the shelf” cassettes to be coupled to the pulley hub 32 and over the freewheel mechanism so that they may be used with the bike trainer 10. Manufacturers of cassettes that may be used with the bike trainer 10 include but are not limited to Shimano, Campagnolo, SRAM, and the like. Further, some embodiments may include “spacers” positionable on the axle 23 and secured by the axle clamp 24 and the axle clamp adjustment 22 to accommodate bicycles having differing spacing between their rear dropouts, such as road bicycles and mountain bicycles. As can be appreciated, the spacers may be also rest freely on the axle 23, may be threaded onto the axle 23, or may otherwise be positioned thereon.

As may best be viewed in FIGS. 2 and 4, the first pulley 12 includes teeth 14 configured to interface with a flexible drive member or belt 16 to provide transmission of power. As shown, the belt 16 is wrapped around a portion of the outer circumference of the first pulley 12 and around a smaller second pulley 18 rotatably coupled to a laterally extending axle 92 (see FIG. 5) positioned at a mid-portion 45 of the frame 40. In the embodiment shown, the second pulley 18 and the axle 92 are integrally formed as a single piece, but this is not required. The ratio of the diameter of the first pulley 12 to the diameter of the second pulley 18 may be between about 4 to 1 and 12 to 1 (e.g., 8 to 1), but it is not so limited. Similar to the first pulley 12, the second pulley 18 includes teeth 20 configured to interface with the belt 16. A fan 80 is coupled to the axle 92, and may be press fit or otherwise secured to the axle 92 on a side of the frame 40 opposite the side of the second pulley 18 and where the bicycle 100 is positioned. In operation, when a user rotates the pedals 110 of the bicycle 100, the belt 16 causes the first pulley 18 to drive the second pulley 18, thereby rotating the fan 80.

As best viewed in FIGS. 4 and 6, an idler/tension pulley 36 is provided to allow a user to selectively adjust the tension of the belt 16. In some embodiments, the tension of the belt 16 is not adjustable by a user. Further, as can be appreciated, in the event where the belt 16 is to be removed, a user may simply adjust the position of the tension pulley 36 to a position wherein the belt 16 is loose enough to be removed from the pulleys 12, 18, and 36. As shown in FIG. 6, the tension pulley 36 is coupled to a tension pulley adjustment 64 that comprises a tension adjusting bolt 68 and an adjustment lock bolt 66. In operation, a user may loosen or tighten the tension adjusting bolt 68 until the tension pulley 36 is in a desired position (and the belt 16 is at a desired tension) and then tighten the adjustment lock bolt 66 to secure the positioning of the tension pulley 36.

The bike trainer 10 is supported by a center support member 58, a laterally extending right support member 56 and a laterally extending left support member 60, which are removably coupled to the frame 40. In the embodiment shown, the left support member 60 and the right support member 56 are integrally formed as a single piece, but this is not a requirement. The support members 56, 58, and 60 also include a total of four pads 62 to provide a stable interface between the bike trainer 10 and a supporting surface (e.g., a floor). One of the pads 62 is positioned near each forward end of each of the support members 56, 58, and 60, and one pad is positioned near the rearward intersection of the left support member 60 and the right support member 56. The height of each of the pads 62 relative to the support members 56, 58, and 60 may be adjustable so that the bike trainer 10 may be sturdily supported by an uneven surface without rocking. As can be appreciated, this configuration provides substantial support to the bike trainer 10 and bicycle 100 when a user is operating the bike trainer 10, such that the user remains stable on the bicycle 100 without rocking during use. It should also be appreciated that the number of pads 62 may be varied as well (e.g., three pads, six pads, or the like).

The support members 56, 58, and 60 are coupled to a lower portion 42 of the frame 40 using one or more fasteners such as screws (not shown). As illustrated, when coupled together, the lower portion 42 of the frame 40 and a lower shell 46 form a hollow interior region sized to receive rearward portions of the support members 56, 58, and 60. One or more fasteners, such as screws, may be used to secure the support members 56, 58, and 60 to the lower shell 46 and to the lower portion 42 of the frame 40. Advantageously, by permitting the support member 56, 58, and 60 to be selectively removed from the remainder of the bike trainer 10, the bike trainer 10 may be relocated and/or shipped more efficiently.

In operation, the fan 80 acts as a flywheel to provide resistance as well as inertia to the bike trainer 10. As the fan 80 rotates at a higher speed, the air resistance provided by a plurality of radially extending fan blades 84 provides relatively more resistance to a user of the bike trainer 10. Further, the fan 80 has a suitable weight such that it has a relatively high moment of inertia, thereby storing a large amount of rotational energy. To further increase the inertia provided by the fan 80 as it rotates, a significant portion of the weight of the fan is disposed at its periphery. This is achieved by an outer band 85 that extends circumferentially around the distal ends of each of the fan blades 84. This inertia provided by the fan 80 allows the bike trainer 10 to provide a feel of “coasting” for a user, such that the energy produced by pedaling is not immediately lost after the user stops pedaling. As can be appreciated, this feature of the present disclosure provides a user with a riding experience that is similar to a moving bicycle.

To provide a suitable amount of inertia, the fan 80 may be formed from ductile iron, steel, or any other material or materials having a relatively high toughness and density. Additionally, the fan 80 may have a weight of about 5 to 25 pounds (e.g., 15 pounds). The moment of inertia of the fan 80 about its spinning axis may be about 220 to 260 pound square inches (lb*in²). Further, as shown best in FIGS. 5 and 7, the fan blades 84 are oriented such that during use air will flow from right to left, that is, from the side of the fan 80 near the frame 40 to the side of the fan spaced apart from the frame 40. Additionally, the shape and positioning of the blades 84 provide suitable resistance without generating a substantial amount of noise, such that the bike trainer 10 is relatively quiet during operation. Another quality resulting from the orientation of the fan blades 84 is that during use the fan 80 is driven toward the frame 40, such that if for some reason the fan 80 came loose, it would be driven toward the frame 40 and not toward the free end. As can be appreciated, this feature may possibly prevent the fan 80 from falling off the axle 92 and coming into contact with objects or persons.

As best shown in FIGS. 1 and 2, the bike trainer 10 may also include a selectively removable cover 48 that is fastened to the mid portion 45 of the frame 40. The cover 48 is operative to cover the second pulley 18, the tension pulley 36, and the tension pulley adjustment 64. The cover 48 includes cover fastener recesses 50 that are aligned with threaded cover fastener apertures 54 (see FIG. 6) in the frame 40. Cover fasteners 52 (e.g., screws) may be used to removably secure the cover 48 to the frame 40.

Additionally, a fan housing 82 may be provided to enclose the fan 80. The fan housing includes a right fan grill 86 and a left fan grill 87. As shown in FIG. 3, the left fan grill 87 may be removably secured to the fan housing 82 by fasteners 90 (e.g., screws). Further, the fan housing 82 may be selectively secured to the lower portion 42 of the frame 40 by a fan housing fastener 88. The fan housing 82 may be formed from any suitable materials (e.g., plastic). As can be appreciated, the fan housing 82 may generally reduce the likelihood of objects coming into contact with the fan 80.

The bike trainer 10 shown and described herein permits a user to simulate the feel and ride of his or her own bicycle, thereby providing a quality workout when riding a bicycle in a conventional manner is undesirable (e.g., poor weather, limited space, or the like). As discussed above, the bike trainer 10 provides a these features by creating a suitable amount of resistance to allow users to get an effective workout, and by providing a freewheel and flywheel mechanism to preserve the rotational energy generated by a user by pedaling a bicycle coupled to the bike trainer 10. Further, by providing a substantial support structure, a user of the bike trainer 10 is sturdily supported on his or her bicycle during use.

Power Measurement Device

FIG. 10 is a left-rear perspective view of the bike trainer 10 and the bicycle 100, wherein a power console unit 200 is coupled to a handlebar 120 of the bicycle, and a velocity sensor 250 is coupled to the upper portion 44 of the frame 40 of the bike trainer. The power console unit 200 may best be viewed in FIG. 11, and the velocity sensor 250 may best be viewed in FIG. 12. As discussed below, the power console unit 200 and the velocity sensor 250 are operative to communicate with each other wirelessly.

As shown in FIG. 11, the power console unit 200 includes a coupling portion 230 configured to selectively and removably couple the power console unit to the handlebar 120 of the bicycle 100. The power console unit 200 illustrated includes an adjustment mechanism or knob 234 operative to allow a user to adjust the positioning (e.g., viewing angle or tilt) of the power console unit 200 to a position that is desired by the user. In some embodiments, the knob 234 or a separate mechanism may permit a user to selectively attach and remove the power console unit 200 from the handlebar 120 or another suitable portion of the bicycle 100.

As shown in FIGS. 11 and 13, the power console unit 200 includes a user interface 208 comprising a display 208A, a plurality of left-side input controls or buttons 208B, and a plurality of right-side input controls or buttons 208C. The display 208A may be configured to display measurement data including power output, cadence, elapsed time, speed, heart rate, distance, and the like. The display 208A may also display statistical measurements (e.g., averages, maximums, etc.) of one or more of the measurement data. The input buttons 208B and 208C are configured to permit the user to control the operation of the power console unit 200. For example, the input buttons 208B and 208C may allow the user to modify the information displayed on the display 208A, to input information to the power console unit 200, or to otherwise control or operate features of the power console unit. The input buttons 208B and 208C may be positioned at various locations on the power console unit 200, and may include various types of input devices including buttons, wheels, keys, touch screens, and the like, or designated portions of the display 208A if a touch screen display.

As shown in FIG. 13, the power console unit 200 also includes a controller 204 operative to control the operation of the power console unit. The controller 204 may be operatively coupled to the user interface 208, a wired or wireless communications interface 212, and one or more sensors including a temperature sensor 216, a humidity sensor 220, and a pressure sensor 224. In some embodiments, one or more of these sensors may be absent or additional sensors may be provided. The controller 204 may include features of microcontrollers known in the art. For example, the controller 204 may include one or more processor cores, one or more types of memory, and input/output peripherals. The controller 204 may be application specific or a generally available controller, provided that it is capable of performing the functionality discussed herein.

The communications interface 212 may be any suitable wired or wireless communications interface. In the illustrated embodiment, the communications interface 212 is a wireless interface. The communications interface 212 may enable the controller 204 to communicate with a variety of input and output devices, including the velocity sensor 250. Further, the controller 204 may be operative to connect to or “pair” with one or several other devices or user interfaces simultaneously using any suitable communications technologies.

In some embodiments, the power console unit 200 is operative to save workout data in one or more file formats (e.g., date/time-stamped comma separated values (CSV) files, or other file types). This saved data may be transferred or downloaded to another computer (e.g., a portable computer, a watch, or the like) in a variety of ways, both wired and wireless. For example, in some embodiments workout data may be downloaded to a computer or other device via USB or by a suitable wireless protocol (e.g., ANT+, or other wireless protocols). Further, in some embodiments, the power console unit 200 may also allow users to review workout data and to upload customized training workouts or programs to the console unit.

As shown in FIG. 12, the velocity sensor 250 is selectively mountable onto the upper portion 44 of the frame 40 of the bike trainer 10. As an example, the user may mount the velocity sensor 250 to the upper portion 44 of the frame 40 using one or more suitable fasteners 252, such as brackets, screws, clamps or the like. In other embodiments, the velocity sensor 250 may be fixedly mounted to or integrated with the frame 40. The velocity sensor 250 is positioned proximate to a left-side surface 13 of the first pulley 12. A magnet 270 is removably or fixedly positioned on the left-side surface 13 of the first pulley 12 such that the magnet passes by the velocity sensor 250 once during each revolution of the first pulley as the bike trainer 10 is operated by a user.

As shown in FIG. 13, the velocity sensor 250 includes a switch 258 configured to operate when in the presence of a magnetic field. These types of switches may generally be referred to as “reed switches.” The switch 258 is operative to toggle each time the magnet 270 passes by the velocity sensor 250 during operation of the bike trainer 10. Thus, the velocity sensor 250 is operative to determine the angular velocity (ω_(p)) of the first pulley 12. Since the first pulley 12 is connected to the fan 80 (see FIG. 5) using the synchronous belt 16 (see FIG. 4) at a fixed gear ratio (e.g., 8:1 ratio), the angular velocity (ω_(f)) of the fan 80 can be determined (e.g., ω_(f)=8*ω_(p)). Although the embodiment described utilizes a reed switch, other embodiments may utilize other switches or mechanisms configured to directly or indirectly determine the angular velocity (ω_(f)) of the fan 80.

The velocity sensor 250 also includes a controller 254 operative to control the operation of the velocity sensor. The controller 254 may be operatively coupled to the switch 258 and a wired or wireless communications interface 262. Like the controller 204, the controller 254 may include one or more processor cores, one or more types of memory, and input/output peripherals. The controller 254 may be application specific or a generally available controller. In general, the controller 254 is operative to receive signals from the switch 258, to determine an instantaneous angular velocity (ω_(p)) of the first pulley 12 (or the angular velocity (ω_(f)) of the fan 80) based on the signals received from the switch, and to send angular velocity measurements to the power console unit 200 wirelessly via the communications interface 262.

The communications interface 262 may be any suitable wired or wireless communications interface. In the illustrated embodiment, the communications interface 262 is a wireless communications interface. The communications interface 262 may enable the controller 254 of the velocity sensor 250 to communicate with a variety of input and output devices, including the power console unit 200. Further, the controller 254 may be operative to connect to or “pair” with one or more other devices or user interfaces simultaneously using any suitable communications technologies.

In operation, the power console unit 200 is configured to receive the angular velocity measurements from the velocity sensor 250 and to calculate the instantaneous output power by inserting the angular velocity measurements into a power equation. The output power may be continuously displayed on the display 208A shown in FIG. 11. As discussed further below, the power equation is periodically modified to account for various environmental and/or mechanical conditions (“operating conditions”) that are known to affect the power output calculations so that more accurate power calculations may be taken. The environmental conditions may be measured using sensors, may be input by users, may be determined during manufacturing or installation, or any combination thereof.

The total output power (P_(TOTAL)) of the bike trainer 10 can be represented as the sum of the power due to the resistance of the fan 80 (P_(R)) and the power due to the kinetic energy of the fan (P_(KE)). That is:

P _(TOTAL) =P _(R) +P _(KE)   (Equation 1)

The power due to the resistance of the fan 80 (P_(R)) comprises a base equation:

P _(R) =Aω _(f) ³ +Bω _(f) ² +Cω _(f)   (Equation 2)

where the coefficients A, B, and C are numerical values that may be derived through empirical testing, and W_(f) is the angular velocity of the fan 80 in radians per second (rad/sec). Thus, the instantaneous P_(R) is a function of the coefficients A, B, and C, and the angular velocity ω_(f) of the fan 80. As discussed above, the angular velocity of the fan 80 is provided to the power console unit 200 by the velocity sensor 250.

The coefficients A and B of Equation 2 account for aerodynamic effects of the air moving over and around the radially extending blades 84 of the fan 80 (see FIG. 5). The coefficient C accounts for the mechanical drag of the bike trainer 10 due to friction forces. As the angular velocity ω_(f) of the fan 80 increases or decreases, the power needed by the user to overcome the resistance power (P_(R)) of the fan 80 increases or decreases, respectively, as determined by Equation 2.

The power due to the kinetic energy (P_(KE)) of the fan 80 is equal to the change of kinetic energy over a period of time. The power due to kinetic energy (P_(KE)) may be represented by the following equation:

P _(KE) =KE _(f) −KE _(fp)   (Equation 3)

where KE_(f) is the present measurement of the kinetic energy of the fan 80, and KE_(fp) is the kinetic energy of the fan 80 measured one second before the present measurement (“previous measurement”). Since kinetic energy is equal to one half of the mass moment of inertia (J) times the angular velocity (ω_(f)) squared, the power of the fan 80 due to kinetic energy may be determined by the following equation:

P _(KE)=(1/2)*J*ω_(f) ²−(1/2)*J*ω _(fp) ²   (Equation 4)

which may be reduced to:

P _(KE)=(1/2)*J*(ω_(f) ²−ω_(fp) ²)   (Equation 5)

In Equations 4 and 5, J is the mass moment of inertia of the fan 80, in kg-m², which is based on the geometry of the fan. The variable W_(f) is the angular velocity of the fan 80, in rad/sec, at the present time (or latest measurement), and the variable ω_(fp) is the angular velocity of the fan at the previous second. Thus, given the angular velocity measurements of the fan 80 each second, the energy (in Watts) required to maintain the fan at that angular velocity may be calculated.

By inserting Equations 2 and 5 into Equation 1, the following equation for the total output power of a user operating the bike trainer 10 is obtained:

P _(TOTAL) =Aω _(f) ³ +Bω _(f) ² +Cω _(f)+(1/2)*J*(ω_(f) ²−ω_(fp) ²)   (Equation 6)

From Equation 6, it is seen that the total output power is dependent on the angular velocity as provided by the velocity sensor 250, and the coefficients A, B, and C.

The equation for the power due to resistance of the fan 80 (Equation 2) accounts for the power required to turn the fan through the air at a specific set of atmospheric conditions. However, as the air conditions change, the power required to turn the fan changes. To account for these changes in air conditions, the power console unit 200 is operative to automatically modify one or more of the coefficients A, B, and C in the output power equation (Equation 6) to provide a more accurate power equation.

As discussed above, the coefficients A and B account for the aerodynamic effects of the air moving over and around the blades 84 of the fan 80. These constants vary as air temperature, humidity, altitude and/or atmospheric pressure change. To compensate for these variables, the power console unit 200 includes the temperature sensor 216, the humidity sensor 220, and the atmospheric pressure sensor 224 (in some embodiments) coupled to the controller 204 (see FIG. 13). In some embodiments, one or more additional sensors may be included, or one or more of the sensors may be omitted. Further, in some embodiments, a user may be able to input one or more environmental conditions into the power console unit 200 via the user interface 208. For example, in one embodiment the user is able to input the altitude of the location of the bike trainer 10 so that the altitude may be used to appropriately adjust the coefficients A and B of the power equation (Equation 6).

The sensors 216, 220, and 224 may be operative to measure changing atmospheric conditions and to provide these measurements to the controller 204 of the power console unit 200 so that the power equation may be automatically adjusted. In this regard, the accuracy of the power console unit 200 is improved by accounting for various types of atmospheric conditions.

As discussed above, the coefficient C in the power equation accounts for the mechanical drag of the bike trainer 10 due to belt/pulley friction and bearing friction. In general, the coefficient C may vary for each bike trainer 10 so it may be determined for each bike trainer during the manufacturing or installation process. Typically, the coefficient C will not change or will change slowly over time so it may not need to be measured and updated as often as the coefficients A and B. To determine an appropriate value for the coefficient C, a “spin-down” test is performed for each bike trainer 10 at low speeds (e.g., less than about 20 kilometers per hour, or the like). The spin down test comprises measuring the time required for the fan 80 of the bike trainer 10 to decelerate between two fixed low speed fan velocities. Based on the result of this test, an appropriate value for the coefficient C may be determined and stored in a memory of the controller 204 of the power console unit 200.

In some embodiments, the atmospheric pressure may be measured using a spin-down test at relatively high fan velocities (e.g., 40 to 45 kph, or the like). Once the atmospheric pressure has been determined using such a high-velocity spin-down test, one or both of the coefficients A and B may be adjusted appropriately dependent on the determined atmospheric pressure.

FIG. 14 illustrates a process 300 for measuring the power output of a user operating the bike trainer 10 using the power console unit 200 and the velocity sensor 250 discussed above. The process 300 begins at step 304 by determining the coefficients A, B, and C for the power equation (Equation 6) for a plurality of expected operating conditions. As discussed above, the coefficients A, B, and C are dependent on a variety of conditions, including temperature, humidity, altitude, atmospheric pressure, and the mechanical drag (e.g., due to friction) of the bike trainer 10. Through empirical testing in controlled environments, the relationships between the values of the coefficients A, B, and C and the various environmental conditions may be determined. In step 308, the relationships are stored in a memory of the controller 204 of the power console unit 200. The relationships between the values of the coefficients A, B, and C and the operating conditions may be stored using any suitable system, including one or more lookup-tables, equations, sets of rules, and the like. An exemplary process for generating the relationships between the values of the coefficients A, B, and C and the operating conditions is discussed below with reference to FIG. 15.

The process 300 continues with step 312 wherein information relating to the environmental or operating conditions is received. As discussed above, this information may be provided from a variety of sources at a variety of times. For example, the mechanical drag of a particular bike trainer may be determined during the manufacturing process using the aforementioned low-speed spin-down test so that the coefficient C may be determined and stored. The temperature, humidity, altitude and/or atmospheric pressure may be measured periodically during use using the sensors 216, 220, and 224 (see FIG. 13), or may be input by a user (e.g., a user may input the altitude or temperature via the user interface 208).

Once the power console unit 200 has received information relating to the environmental and operating conditions, the power equation (Equation 6) may be generated or modified by determining the coefficients A, B, and C using the empirically derived relationships between the coefficients and operating conditions, step 316. As can be appreciated, the coefficients of the power equation may be automatically adjusted periodically (e.g., once per second, once per day, or the like) as the operating conditions are changed or updated by the sensors 216, 220, and 224 or input by the user. Further, each of the coefficients may be adjusted independently of the others.

As the user operates the bike trainer 10, the velocity sensor 250 will periodically (e.g., once per second) send measurements indicative of the angular velocity (ω_(f)) of the fan 80 to the power console unit 200, step 320. In some embodiments, the velocity sensor 250 may send measurements of the angular velocity (ω_(p)) of the first pulley 12 rather than of the fan 80. In this case, the power console unit 200 may convert the angular velocity ω_(p) to ω_(f) using the known fixed gear ratio (e.g., 8:1) between the first pulley 12 and the fan 80.

The power console unit 200 may then periodically calculate the instantaneous power output of the bike trainer 10 as the user operates the bike trainer by solving the power equation (Equation 6) using the received angular velocity measurements, step 324. In step 328, the calculated output power may be continuously displayed on the display 208A (see FIG. 11) of the power console unit 200. As discussed above, the power console unit 200 may also be configured to display various statistical measurements of the output power, including average output power, maximum output power, and the like.

FIG. 15 depicts a process 350 for empirically determining the coefficients A, B, and C of the power equation (Equation 6) as a function of various expected operating conditions. The process 350 begins at block 352 wherein a torque or power measurement device is coupled to the pedals 110 of the bicycle 100, which is in turn coupled to the bike trainer 10. Next, using the torque measurement device, the output power is measured at a variety of operating conditions that vary with regard to atmospheric pressure (or altitude), humidity, temperature, and mechanical properties for a particular bike trainer 10, block 354. Using the results of the power measurements taken at the variety of operating conditions, equations for the coefficients A, B, and C may be generated and stored in a memory, blocks 356 and 358.

Exemplary coefficient equations for the bike trainer 10 are provided below. A suitable coefficient equation for the coefficient A may be:

A=((0.348444*P)−H*(0.00252*T−0.020582))/(273.15+T)/1.2*0.00715   (Equation 7)

where P is air pressure, and is related to altitude by the following equation:

P=1026.8−(Altitude in meters)/8 millibars   (Equation 8)

(i.e., an air pressure drop of 1 millibar for every 8 meters gain in altitude). H is relative humidity expressed as a decimal (e.g., 0.0 being 0% relative humidity and 1.0 being 100% relative humidity), and T is the temperature in degrees Celsius. The division by 1.2 in Equation 7 is provided to normalize the air density to conditions present on testing day and has units of kg/m³.

A suitable coefficient equation for the coefficient B may be:

((0.0026*T+0.9487)*(−0.0322))   (Equation 9)

As discussed above, the coefficient C is dependent upon the mechanical drag of a particular bike trainer 10, and may be determined using a spin-down test at low speeds. A suitable coefficient equation for the C coefficient may be:

(3.2349*C_(SD))   (Equation 10)

where C_(SD) is a spin-down correction determined by the following equation:

C _(SD)=(ΔV _(flywheel) /ΔT)/3.343   (Equation 11)

where ΔV_(flywheel) the change of angular velocity of the flywheel in rad/sec and ΔT is the time in seconds for ΔV_(flywheel) to be approximately 71 rad/sec. The 3.343 multiplier is used to normalize Equation 11 to the particular bike trainer 10 that was tested.

As discussed above, embodiments of the present invention utilize a power output equation that models the power due to the resistance of the fan 80 as well as the power due to kinetic energy of the fan. Further, by modifying the power equation periodically to account for environmental and operating conditions, the power console unit 200 is operative to provide a user with very accurate power output measurements. This can be advantageous for users, especially elite athletes, that desire to measure their training level and progress precisely.

The foregoing described embodiments depict different components contained within, or connected with, different other components. It is to be understood that such depicted architectures are merely exemplary, and that in fact many other architectures can be implemented which achieve the same functionality. In a conceptual sense, any arrangement of components to achieve the same functionality is effectively “associated” such that the desired functionality is achieved. Hence, any two components herein combined to achieve a particular functionality can be seen as “associated with” each other such that the desired functionality is achieved, irrespective of architectures or intermedial components. Likewise, any two components so associated can also be viewed as being “operably connected”, or “operably coupled”, to each other to achieve the desired functionality.

While particular embodiments of the present invention have been shown and described, it will be obvious to those skilled in the art that, based upon the teachings herein, changes and modifications may be made without departing from this invention and its broader aspects and, therefore, the appended claims are to encompass within their scope all such changes and modifications as are within the true spirit and scope of this invention.

Furthermore, it is to be understood that the invention is solely defined by the appended claims. It will be understood by those within the art that, in general, terms used herein, and especially in the appended claims (e.g., bodies of the appended claims) are generally intended as “open” terms (e.g., the term “including” should be interpreted as “including but not limited to,” the term “having” should be interpreted as “having at least,” the term “includes” should be interpreted as “includes but is not limited to,” etc.).

It will be further understood by those within the art that if a specific number of an introduced claim recitation is intended, such an intent will be explicitly recited in the claim, and in the absence of such recitation no such intent is present. For example, as an aid to understanding, the following appended claims may contain usage of the introductory phrases “at least one” and “one or more” to introduce claim recitations. However, the use of such phrases should not be construed to imply that the introduction of a claim recitation by the indefinite articles “a” or “an” limits any particular claim containing such introduced claim recitation to inventions containing only one such recitation, even when the same claim includes the introductory phrases “one or more” or “at least one” and indefinite articles such as “a” or “an” (e.g., “a” and/or “an” should typically be interpreted to mean “at least one” or “one or more”); the same holds true for the use of definite articles used to introduce claim recitations. In addition, even if a specific number of an introduced claim recitation is explicitly recited, those skilled in the art will recognize that such recitation should typically be interpreted to mean at least the recited number (e.g., the bare recitation of “two recitations,” without other modifiers, typically means at least two recitations, or two or more recitations).

Accordingly, the invention is not limited except as by the appended claims. 

1. A power measurement device for a bike trainer, the bike trainer being usable as a training device when coupled to a conventional bicycle, the bike trainer comprising a fan rotatably coupled to the bicycle through a freewheel mechanism, the power measurement device comprising: a velocity sensor operative to obtain measurements indicative of the angular velocity of the fan; and a power console unit operative to receive measurements from the velocity sensor and, based on the received measurements, to calculate an output power of a user operating the bike trainer dependent an operating condition of the bike trainer and the kinetic energy of the fan.
 2. The power measurement device of claim 1, wherein the power console unit is operative to receive measurements from the velocity sensor wirelessly.
 3. The power measurement device of claim 1, wherein the power console unit further comprises a display operative to display the calculated output power.
 4. The power measurement device of claim 1, wherein the power console unit comprises a sensor operative to sense one or more operating conditions of the bike trainer, and wherein the power console unit is operative to receive signals from the sensor, and to modify the output power calculation dependent on the received signals.
 5. The power measurement device of claim 4, wherein the sensor comprises one of a temperature sensor, a humidity sensor, and an air pressure sensor.
 6. The power measurement device of claim 1, wherein the operating condition includes temperature, atmospheric pressure, or humidity.
 7. The power measurement device of claim 1, wherein the operating condition includes mechanical drag of the bike trainer.
 8. The power measurement device of claim 7, wherein the mechanical drag of the bike trainer is determined by measuring the time required for the fan to spin down from a first angular velocity to a second, lower angular velocity.
 9. The power measurement device of claim 1, wherein the operating condition includes atmospheric pressure, and wherein the power console unit comprises an input device operative to allow a user to input an altitude value.
 10. The power measurement device of claim 1, wherein the power console unit comprises an input device operative to allow a user to input one or more operating conditions of the bike trainer.
 11. The power measurement device of claim 10, wherein the input device is operative to allow a user to input an altitude value of the bike trainer, and wherein the power console unit is operative to calculate the output power of the bike trainer dependent upon the altitude value.
 12. The power measurement device of claim 1, further comprising at least two sensors operative to sense two or more operating conditions of the bike trainer, wherein the power console unit is operative to calculate the output power of the bike trainer by utilizing a power equation that is modified dependent on the sensed operating conditions.
 13. The power measurement device of claim 12, wherein the power equation takes into account both power due to air resistance of the fan and due to the kinetic energy of the fan.
 14. A power measurement device for a bike trainer, the bike trainer being usable as a training device when coupled to a conventional bicycle having its rear wheel removed, the bicycle including a frame that includes rear dropouts, the bike trainer comprising: a frame; a first drive member rotatably mounted on a first side of the frame on a laterally extending first axle, the first axle being configured for selective coupling with the rear dropouts of the bicycle; a freewheel mechanism including a first portion engaged with the first drive member, the freewheel mechanism further including a second portion engaged with a sprocket configured to interface with a chain of the bicycle when the bicycle is coupled to the bike trainer, wherein the freewheel mechanism is operative to disengage the first portion from the second portion when the first portion rotates faster than the second portion in a forward direction; a second drive member rotatably mounted on a first side of the frame on a laterally extending second axle; a flexible drive member in driving engagement with and extending between the first drive member and the second drive member; and a fan rotatably mounted on the second axle on a second side of the frame opposite the first side; the power measurement device comprising: a velocity sensor operative to obtain measurements indicative of the angular velocity of the fan; and a power console unit operative to receive measurements from the velocity sensor and, based on the measurements, to calculate an output power of a user operating the bike trainer dependent on an operating condition of the bike trainer and the kinetic energy of the fan.
 15. The power measurement device of claim 14, wherein the power console unit further comprises a display operative to display the calculated output power to a user.
 16. The power measurement device of claim 14, wherein the power console unit comprises a sensor operative to sense one or more operating conditions of the bike trainer, and wherein the power console unit is operative to receive signals from the sensor, and to modify the output power calculation dependent on the received signals.
 17. The power measurement device of claim 16, wherein the sensor comprises one of a temperature sensor and a humidity sensor.
 18. The power measurement device of claim 14, wherein the operating condition includes temperature, atmospheric pressure, or humidity.
 19. The power measurement device of claim 14, wherein the operating condition include mechanical drag of the bike trainer
 20. The power measurement device of claim 14, wherein the power console unit comprises an input device operative to allow a user to input one or more operating conditions of the bike trainer.
 21. The power measurement device of claim 14, further comprising at least two sensors operative to sense two or more operating conditions of the bike trainer, wherein the power console unit is operative to calculate the output power of the bike trainer by utilizing a power equation that is modified dependent on the sensed operating conditions.
 22. The power measurement device of claim 21, wherein the power equation takes into account both power due to resistance of the fan and due to the kinetic energy of the fan.
 23. A method for measuring the power output of a user operating a bike trainer, the bike trainer being usable as a training device when coupled to a conventional bicycle, the bike trainer comprising a fan rotatably coupled to the bicycle through a freewheel mechanism, the method comprising: measuring the angular velocity of the fan as a user operates the bike trainer; and calculating an output power of the user operating the bike trainer dependent on an operating condition of the bike trainer and the kinetic energy of the fan.
 24. The method of claim 23, further comprising receiving the angular velocity measurements at a power console unit wirelessly.
 25. The method of claim 23, further comprising displaying the calculated output power.
 26. The method of claim 23, further comprising sensing one or more operating conditions of the bike trainer, and modifying the output power calculation dependent on the one or more sensed operating conditions.
 27. The method of claim 26, wherein sensing one or more of the operating conditions comprises sensing temperature, sensing humidity, or sensing air pressure.
 28. The method of claim 23, further comprising determining the mechanical drag of the bike trainer by measuring the time required for the fan to spin down from a first angular velocity to a second, lower angular velocity.
 29. The method of claim 23, further comprising receiving input from the user indicative of one or more operating conditions of the bike trainer.
 30. The method of claim 23, further comprising sensing one or more operating conditions of the bike trainer, and calculating the output power by utilizing a power equation that is modified dependent on the sensed operating conditions. 